Web Posted on: February 24, 1998
EVERYTHING YOU NEED TO KNOW ABOUT ENVIRONMENTAL CONTROL UNITS
Patti Lindstrom, OTR
Assistive Technology Program
Rehabilitation Institute of Michigan
261 Mack Blvd.
Detroit, MI, 48201
Voice/Message: 313-745-9885
Fax: 313-993-0543
E-mail: cheezhed1@juno.com
Ghassan Souri, M.S., RE
Assistive Technology Program
Rehabilitation Institute of Michigan
261 Mack Blvd.
Detroit, MI 48201
Voice/Message: 313-745-9885
Fax: 313-993-0543
E-mail: gsouri@juno.com
Living with a severe disability can be devastating. The loss of independence and control of one's environment can lead to low self-esteem and depression. Using an environmental control unit to increase independence and control can improve a person's self esteem by allowing them to participate in every day living, school, work, and leisure activities. This increased independence can reduce the need for a paid attendant, cut down on demands of the family, and provide some much-needed privacy for the individual with a disability.
An Environmental Control Unit (ECU) is any piece of equipment that allows an individual with a disability to control aspects of their environment that are operated by electricity (i.e. lights, TV, telephone, etc.). It is made up of four basic components:
the input method, menu, processor and activity output. The input method is the interface between the human user and the processor. This is how the user will access the unit. The menu displays the present status of the system and helps in the selection of the commands. The processor consists of the electronic that process the command and execute the action. The activity output consists of the devices that will be controlled (lights, TV, telephone, etc.) and any additional modules necessary to carry out the action.
Environmental Control Units can be divided into two types: computer based, and stand-alone. A computer-based system consists of a software program and the necessary peripherals that allow a computer to function as an ECU. The advantages to using this type of system are the relatively low cost (the software plus a personal computer is cheaper than most stand-alone units) and a predetermined access method if the user already accesses the computer. Disadvantages include the need to have the computer running at all times, the need for visual and/or physical access to the computer from various positions, and the lack of transportability of the system. The system can be made more transportable by using a laptop computer instead of a personal computer.
However, placement of the laptop computer for viewing and access in different environments becomes an issue.
Stand-alone ECUs contain their own electronics and do not utilize a computer to function. Many of these units can be activated by a switch, which acts as the interface between the user and the unit. The switch can be a single switch (button, leaf, etc.) or a dual switch (sip and puff, rocker, etc.). The switch is used to activate a scan of the menu items or commands. The scan can be automatic or directed. Automatic scanning is when the user activates the switch to start the scan and the menu items continue to scan until the user activates the switch to make a selection. This can be done with a single or dual switch. Directed scanning involves multiple activations of the switch to move through the menu until the desired command is located and activated. This can also be done with a single or dual switch.
Some ECUs can be activated by voice commands. These systems are user dependent, which means that the user trains the unit to his or her voice and that user is the only person who can use the system. The ECU creates a bank of voice models from the training. It then compares the voice commands to the bank of models, and when it finds a match, executes the designated action. An advantage to using voice commands to control the ECU is that the user need not have a consistent physical movement. However, they do need to have a consistent voice pattern. Even with a consistent voice pattern, recognition accuracy is less than 100 percent and the accuracy decreases even more in a noisy environment. The user also needs to have adequate memory skills to remember the command sequence unless he or she has visual access to a display.
All ECUs transmit signals to the devices that will be controlled. House wiring, ultrasound, infrared (IR), or radio frequency (RF) can transmit these signals. Using house wiring, digital control signals are transmitted over the existing house wiring from the ECU to individual appliance modules, which are plugged into the standard electrical outlet. Each module contains a receiver that can interpret the codes sent out by the ECU. Each appliance to be controlled is plugged into a module that is then plugged into the wall. The major advantage of house wiring transmission is the lack of installation costs since existing wiring is used. Disadvantages include possible interference between systems on the same electrical power system (i.e. in an apartment building), and lack of portability.
Ultrasound transmission uses sound waves that are too high in frequency (40,000 Hz) to be heard by humans. These signals are transmitted through the air to a receiver located up to several hundred feet from the ECU. Solid objects can block ultrasound waves so it is important to have a clear path between the ECU and the receiver. The major advantage of ultrasound transmission is that it is highly portable, since it is easy to unplug the receiver modules and move them to a new location.
Another mode of transmission is the use of infrared light (IR). This is most common in the control of home electronics (TV, VCR, stereo, etc.) by remote control. Some ECUs can learn the IR signals of various remote controls so that the ECU can control those appliances. The major advantages of using IR devices are ease of portability and no installation costs. A major disadvantage is that the signal can be blocked easily so the ECU and receiver must be in the same room (unless additional equipment is used).
The last method of transmission is the use of radio frequency (rf) waves. The most common example of this type of remote control is garage door openers and cordless telephones. The major advantage of radio frequency transmission is that it is not blocked doors or walls and transmission can be over a relatively long distance. A major disadvantage is the possibility of interference with other rf signals. This possibility can be reduced by decreasing the distance between the ECU and the receiver and
by having several transmission channels available.
Several variables should be considered by clinicians when evaluating a client for an ECU. These variables include:
Input (Access): Can the user effectively operate the available input (access) method(s)? Are the input (access) method(s) reliable and repeatable? Can the input (access) method be modified to accommodate changes in the user's condition? Capabilities of the ECU: Does the ECU offer control of all the devices/functions that the user wants to control?
Ease of Learning: Can the user handle the memory and sequencing requirements? Is the method of operation intuitive, logical and easy to learn?
Modularity: Can the system start with a single function and expand into a full system at a later time? Can the user exclude functions that he/she does not need?
Multiple Control Base Sites: Can the system be operated from a wheelchair as well as from bed and from different rooms?
Choice of Wheelchair Access Mode: Can the system be used through the wheelchair's ECU port using the same input device used to drive the chair?
Feedback: Can the user adjust the ECU feedback to accommodate specific needs (e.g. vision or hearing problems). Is the feedback reliable and recognizable?
Menu: Are choices presented in an understandable way? Is the entire menu visible at all times so the user can see all options?
Direct Connection: Does the ECU provide for the operation of electrical devices by direct connection or there is a need for an X-10 transmitter?
Cost: Consider which system gives you the most function per dollar? Which is the best VALUE?
Accessory Accommodation: Will the system accommodate the addition of accessories to control additional functions?
Customization: Can the system be customized to meet the unique needs of a specific user?
Other: Is a battery back up available? Will the ECU interface with other assistive technology equipment such as computers or communication aids? Does the manufacturer offer warranty and service?
Bain B, Leger D: "Assistive Technology, an Interdisciplinary Approach." Churchill Livingstone, 1997.
Cook A, Hussey S: "Assistive Technologies: Principles and Practice." Mosby-Year Book, St. Louis, MO, 1995.
Selection Guidelines for Environmental Control Systems, APT Technology, Inc. (1997).